deriveDarkVariant
deriveDarkVariant(
lightColor):string
A client-only heuristic for pre-filling a dark-mode color from a light one — spec
955-forms-look-and-feel. Used by a settings UI (ebitex’s own hosted-page/embed look-and-feel
settings, or any third-party consumer building their own) to suggest a starting dark value the
moment a light color is picked, before the organization ever saves; the suggestion is always
editable afterward. Deliberately the only place this derivation exists — Forms.Api never
computes one, it only ever stores what it’s given (see SPEC.md’s Business Logic) — so there is
exactly one implementation to keep correct, not two kept in sync across languages.
Only understands #rrggbb hex, which is what a native <input type="color"> produces and
therefore what any color-picker-driven settings UI will actually pass in. A non-hex CSS color
string (oklch(...), a named color, transparent, …) is returned unchanged — deriving a dark
variant of an arbitrary CSS color generically needs a real color-management library, which this
zero-runtime-dependency package deliberately doesn’t carry (see README’s “no font stack, no
imposed max-width” posture, one level up).
Parameters
Section titled “Parameters”lightColor
Section titled “lightColor”string
Returns
Section titled “Returns”string